The invention relates in general to electronic circuits and more specifically to differential signal amplifiers.
Differential signal amplifiers amplify a differential signal to form an amplified differential output signal and can be used for a variety of purposes and within different types of circuits. The differential signal amplifier produces a differential output signal from a differential input signal that includes two signals where each of the two signals is complementary to the other. Typical uses of differential signal amplifiers include using an amplifier with a gain greater than 1 to increase the amplitude of the input signal. Several differential signal amplifiers may be connected to form an amplifier with a higher gain. Other uses include using the amplifier as a buffer between circuits. Applications for differential signal amplifiers include uses within current mode logic (CML) circuits. Another example includes high frequency postamplifiers for use in high speed circuits such as SONET transceivers. Complementary Metal Oxide Semiconductor (CMOS) techniques are often used to manufacture the amplifiers.
In order to achieve high frequency performance in CMOS differential signal amplifiers, conventional techniques result in increased power dissipation within the amplifiers. Conventional amplifiers designs include biasing the transistors of the amplifier such that the DC current is increased. Conventional designs, therefore, result in circuits having increased power dissipation. Further, conventional circuits may not meet bandwidth requirements even if the DC current is increased to a maximum.
Therefore, there is a need for an efficient differential signal amplifier with increased high frequency performance.
In an exemplary embodiment, a wide-bandwidth amplifier includes a pair of transistors having output ports connected to two current sources and an impedance element connected between the output ports. The impedance element creates a zero resulting a wide-bandwidth frequency response of the amplifier.